I noticed in on of the posts that some engines(Onans) have loose valve seats when cold. You need to correct this problem soon before it causes worse problems. The fix is fairly simple. Remove the head and then with the valves in the closed position and the valve seats fully seated, use a center punch and stake the seats in place. Usually about 8 or more stakes per seat, depending on valve size. It is a good idea to lap the valves after doing this. If the valve seats float they will eventually erode the block and the the seats will never stay in place. B&S had this problem about 10 years ago when they accidentally assembled "green" blocks(not fully cured after casting). Also as the block wears from a floating valve seat your valve clearence will change.